_In any one and the same sort of Rays, emerging in any Angle out of any
refracting Surface into one and the same Medium, the Interval of the
following Fits of easy Reflexion and Transmission are either accurately
or very nearly, as the Rectangle of the Secant of the Angle of
Refraction, and of the Secant of another Angle, whose Sine is the first
of 106 arithmetical mean Proportionals, between the Sines of Incidence
and Refraction, counted from the Sine of Refraction._
This is manifest by the 7th and 19th Observations.